1. Field of the Invention
The present invention relates to a cation exchange membrane and an electrolytic cell using thereof. More particularly, it relates to a cation exchange membrane and an electrolytic cell using thereof suitable for an electrolysis of water or an aqueous solution of an acid, a base, an alkali metal halide or an alkali metal carbonate.
2. Description of the Prior Art
As a process for producing an alkali metal hydroxide and chlorine by an electrolysis of an aqueous solution of an alkali metal chloride, a diaphragm method has been mainly employed instead of a mercury method in view of a prevention of a public pollution. Moreover, an ion exchange membrane method has been practically operated to produce an alkali metal hydroxide having high concentration in high purity
On the other hand, in view of energy saving, it has required to minimize a cell voltage in such electrolysis. Various processes have been proposed, however, the purpose has not been satisfactorily attained since the effect for reduction of the cell voltage has not been satisfactory or the cell has been complicated.
The inventors have studied to operate an electrolysis of an aqueous solution at a minimized load voltage and have found that the purpose has been satisfactorily attained by using a cation exchange membrane having a gas and liquid permeable porous non-electrode layer on at least one of surfaces of the cation exchange membrane facing to an anode or a cathode which is proposed in European Patent Publication No. 0029751 or U.S. Ser. No. 205,567.
The effect for reducing a cell voltage by the use of the cation exchange membrane having such porous layer on the surface is depending upon a kind of the material, a porosity and a thickness of the porous layer. Thus, it is surprising phenomenon that the effect for reducing a cell voltage is attained even by the use of the porous layer made of a non-conductive material. The effect for reducing a cell voltage is also attained even though electrodes are placed with a gap from the membrane without contacting the electrode to the membrane, although the extent of the effect is not remarkable.